I'm real happy with the Ety MC5's. They are just a tad longer than the er6i's, but work fine.
Tips from the ER6i's fit on them - so you can get the same fit and isolation.
I'm told the HF 5's are 'better'.
This morning was my first ride with the mc5. Nice! I used the foam tip and they sealed well; more outside sound compared to the orange foam earplugs, but OK. Great sound and no problem getting a tight fitting helmet on/off. They work.